The objective of this proposal is the study of the non-immune interaction of an oral streptococcal cell wall surface component with the Fc region of normal mammalian IgG. The primary function of this study will then be the evaluation of this interaction as a means by which streptococci potentiate inflammatory disease processes within the oral cavity. The study of this interaction will be approached in the following manner; 1) The prevalence and expression of the IgC(Fc) reactive component by four oral streptococcal species (S. sanguis, S. Salivarius, S. mitis and S. mutans) will be determined; 2) The streptococcal IgG (Fc) reactive component will be extracted from the bacterial surface, isolated and prepared in purified form; 3) The purified IgG (Fc) reactive streptococcal component will be reacted with mammalian IgG and complement fixation and activation assessed in vitro; 4) The inflammatory potential of the IgG (Fc) reactive streptococcal component and IgG will be assessed in vivo by the induction of localized Arthus type reactive and experimental induction of periodontal disease; 5) The functional significance of bacterial bound IgG (Fc) reactive streptococcal component as a suppressor of immune clearance will be evaluated. This study is designed to investigate the potential role of the IgG (Fc) reactive component in the establishment and development of oral inflammation. As such, the proposal will clearly determine the inflammation potential of the interaction of the purified bacterial component with mammalian IgG and complement, but also the proposal will investigate a mechanism (mediated by streptococcal IgG (Fc) reactive component) by which the streptococcus can establish itself in the ecological niche of the mouth. Major emphasis will be placed on the interaction of this bacterial component with host immune constituents and the use of these constituents to the selective advantage of the invading bacterium.